Somewhere along the continuum (perhaps circa 2008 or thereabouts), transporting empty shipping containers back across the Pacific seemed too expensive, so they sold them for relatively low prices and people repurposed them like crazy.
Yes, I remember that the shipping containers were repurposed elsewhere.
At one point, preppers were using containers to build subterranean shelters, storm shelters, and root cellers.
After the earthquakes in Christchurch, New Zealand, the surface containers were repurposed to replace damaged residential housing, pending building repairs.
The containers do represent good temporary housing, but are structurally weak as reinforcement is primarily found only on the corners
therefore they are not really suitable for most subterranean structures due to side crushing from heavy soils, or exposure to high moisture/ flooding.
I have no idea what the market is now for shipping containers, but they do have promise for an inventive mind.